The present invention relates to writing implements including ballpoint pens, cosmetic applicators, marking pens such as sign pens, plastic pens, paint markers, etc.
Conventional writing implements are adapted to prevent the ink from drying by closing the forward end of the implement with a cap while the implement is not in use. However, implements of the type having the cap are inefficient to use, while the cap is likely to become lost. Accordingly, writing implements are developed in recent years which are adapted to automatically close the forward end when brought out of use to eliminate the need for the cap.
For example, Examined Japanese Utility Model Publication SHO No. 42-21538 and Unexamined Japanese Utility Model Publication SHO No. 62-87882 disclose writing implements which comprise a sleeve formed by a magnet and disposed at a forward end portion of the body of the implement, a forward end portion of a barrel including a writing nib and an ink reservoir, such as ballpoint pen refill, retractably projectable forward from the sleeve through a bore extending therethrough, and a closure in the form of a ball or plate and magnetically attractable to the forward end face of the sleeve to close the bore with the closure when the forward end portion of the barrel is in its retracted position. Thus, the writing liquid inside the implement can be automatically prevented from evaporating with the closure without using a cap or the like.
Examined Japanese Utility Model Publications SHO No. 38-18620 and SHO 41-13855 disclose an arrangement wherein the closure is connected to the sleeve by an elastic member, which presses the closure into contact with the forward end face of the sleeve with its elastic force to close the sleeve bore.
However, with the writing implements disclosed in the Examined Japanese Utility Model Publicaiton SHO No. 42-21538 and the Unexamined Japanese Utility Model Publication SHO No. 62-87882, the closure is attracted to the sleeve, only with the magnetic force of the sleeve, so that it is likely that the closure will not fully return to the original closing position, failing to completly close the bore, for example, after the closure is raised through more than 90 degrees when the forward end portion of the barrel is projected forward, or when the barrel is retracted to its stowed position with the implement directed downward. Especially when the barrel is moved forward with the forward end of the implement directed downward, the closure forced away from the sleeve is likely to close the forward end opening of the implement to thereby impede the projection of the barrel end. If the implement is forcibly projected, a great load will act on the barrel end to result in a break.
On the other hand, with the writing implements disclosed in Utility Model Publications SHO No. 38-18620 and SHO 41-13855, the closure is pressed against the sleeve with the elastic restoring force of the elastic member, so that a considerably great restoring force is required of the elastic member to completely close the implement. In the case of the disclosed arrangement, therefore, the barrel end, when to be projected, encounters great resistance offered by the elastic member. Since this resistance increases as the elastic member deforms to a greater extent, an increased load acts on the tip of the implement to break the tip. Conversely, when the elastic restoring force of the elastic member is small, the implement is not closed completely. Consequently, the enclosing space of the sleeve, in which the forward end portion of the barrel is placed, cannot have a desired vapor pressure. This leads to a problem that a greater amount of ink evaporates from the forward end portion of the barrel, and blurred writing occurs.